1. Field of the Invention
The present invention relates generally to position determination in a three-dimensional space effected using impulse radio equipment and methods. Still more particularly the present invention provides a system and method for determining position of mobile units attached to objects or to people within a three-dimensional space. The locating may be carried out from mobile units, from fixed units or from a combination of mobile and fixed units.
The apparatus and method of the present invention are particularly useful for keeping track of rental equipment being used within the three-dimensional space or about to leave the three-dimensional space. Further useful application of the present invention are provision of location information for display to persons traveling about within the three-dimensional space and locating persons lost within the three-dimensional space. One example of a useful such application is persons using facilities of a ski resort. The apparatus and method of the present invention can be employed to provide location information to human operators, such as skiers, to keep from becoming lost. Perhaps most important, the compact lightweight nature of the apparatus of the present invention, and the ability to locate persons in three dimensions from mobile units (such as ski patrol or other rescue personnel) affords a ready capability to find persons buried by an avalanche in time to rescue them alive.
There is a need for a locating apparatus and method that provides lightweight, robust and reliable mobility with a capability for locating objects and people in a three-dimensional space of geographic proportions, such as a ski resort.
2. Related Art
Recent advances in communications technology have enabled an emerging, revolutionary ultra wideband technology (UWB) called impulse radio communications systems (hereinafter called impulse radio).
Impulse radio was first fully described in a series of patents, including U.S. Pat. Nos. 4,641,317 (issued Feb. 3, 1987), U.S. Pat. No. 4,813,057 (issued Mar. 14, 1989), U.S. Pat. No. 4,979,186 (issued Dec. 18, 1990) and U.S. Pat. No. 5,363,108 (issued Nov. 8, 1994) to Larry W. Fullerton. A second generation of impulse radio patents include U.S. Pat. Nos. 5,677,927 (issued Oct. 14, 1997) to Fullerton et al; and U.S. Pat. No. 5,687,169 (issued Nov. 11, 1997) and U.S. Pat. No. 5,832,035 (issued Nov. 3, 1998) to Fullerton. These patent documents are incorporated herein by reference.
Uses of impulse radio systems are described in U.S. patent application Ser. No. 09/332,502, entitled, xe2x80x9cSystem and Method for Intrusion Detection Using a Time Domain Radar Array,xe2x80x9d and U.S. patent application Ser. No. 09/332,503, entitled, xe2x80x9cWide Area Time Domain Radar Array,xe2x80x9d both filed the same day as the present application, Jun. 14, 1999, both of which are assigned to the assignee of the present invention, and both of which are incorporated herein by reference.
Basic impulse radio transmitters emit short pulses approaching a Gaussian monocycle with tightly controlled pulse-to-pulse intervals. Impulse radio systems typically use pulse position modulation, which is a form of time modulation where the value of each instantaneous sample of a modulating signal is caused to modulate the position of a pulse in time.
For impulse radio communications, the pulse-to-pulse interval is varied on a pulse-by-pulse basis by two components: an information component and a pseudo-random code component. Unlike direct sequence spread spectrum systems, the pseudo-random code for impulse radio communications is not necessary for energy spreading because the monocycle pulses themselves have an inherently wide bandwidth. Instead, the pseudo-random code of an impulse radio system is used for channelization, energy smoothing in the frequency domain and for interference suppression.
Generally speaking, an impulse radio receiver is a direct conversion receiver with a cross correlator front end. The front end coherently converts an electromagnetic pulse train of monocycle pulses to a baseband signal in a single stage. The data rate of the impulse radio transmission is typically a fraction of the periodic timing signal used as a time base. Because each data bit modulates the time position of many pulses of the periodic timing signal, this yields a modulated, coded timing signal that comprises a train of identically shaped pulses for each single data bit. The impulse radio receiver integrates multiple pulses to recover the transmitted information.
In a multi-user environment, impulse radio depends, in part, on processing gain to achieve rejection of unwanted signals. Because of the extremely high processing gain achievable with impulse radio, much higher dynamic ranges are possible than are commonly achieved with other spread spectrum methods, some of which must use power control in order to have a viable system. Further, if power is kept to a minimum in an impulse radio system, this will allow closer operation in co-site or nearly co-site situations where two impulse radios must operate concurrently, or where an impulse radio and a narrow band radio must operate close by one another and share the same band.
In some multi-user environments where there is a high density of users in a coverage area or where data rates are so high that processing gain is marginal, power control may be used to reduce the multi-user background noise to improve the number of channels available and the aggregate traffic density of the area.
Other sources of noise, or electromagnetic interference, may also interfere with efficient communication using impulse radio technology. In communicating voice messages, data messages, control messages, or other types of messages, interference causes problems by corrupting information intended to be conveyed by the transmission message.
There is a need for mitigating the effects of electromagnetic interference, or noise, in communication using impulse radio.
In particular, there is a need for mitigating the effects of electromagnetic interference having various characteristics in communication using impulse radio.
A system for locating a plurality of objects in a three-dimensional coordinate system comprises: (a) an impulse radio network including at least three reference impulse radio units and at least one mobile position indicating apparatus; position information relating the reference impulse radio units is recorded by at least one indicating reference impulse radio unit; the reference impulse radio units being in mutual communication; and (b) an affixing structure for affixing a respective mobile position indicating apparatus with a respective object. A respective mobile position indicating apparatus transmits an impulse radio identifying signal that is received by at least one receiving reference impulse radio unit. At least one indicating reference impulse radio unit cooperates with the receiving reference impulse radio unit in using the identifying signal for developing coordinate information for locating the respective mobile position indicating apparatus.
The method comprises the steps of: (a) providing an impulse radio network including at least three reference impulse radio units and at least one mobile position indicating apparatus; position information relating the reference impulse radio units is recorded by at least one indicating reference impulse radio unit; the reference impulse radio units are in mutual communication; (b) providing an affixing structure for affixing a respective mobile position indicating apparatus with a respective object; (c) transmitting an impulse radio identifying signal from a respective mobile position indicating apparatus; (d) Receiving the identifying signal by at least one receiving reference impulse radio unit; and (e) operating at least one indicating reference impulse radio unit in cooperation with the receiving reference impulse radio unit to develop coordinate information for determining the locating of the respective mobile position indicating apparatus.
It is therefore an object of the present invention to provide an apparatus and method for locating objects and people in a three-dimensional space that is lightweight, robust and mobile.
It is a further object of the present invention to provide an apparatus and method for locating objects and people in a three-dimensional space that may be operated from mobile or fixed sites.